Hello Community, We are trying to add user defined scalar functions. Can these functions be used in star tree index for pre-aggregation ?

Scalar functions are one to one. Aggregation Functions are many to one. you will have to implement

public interface AggregationFunction<IntermediateResult, FinalResult extends Comparable>

Thanks @User. Does the star tree index support custom aggregate functions ?

yes, you will have to implement the interface I pasted above and have that available in class path